Avro ReflectDatumWriter中的NullPointerException

superbeeny 发表于 Dev

超级蜜蜂

我对Java对象的Avro序列化有一个特定的问题。我有从xsd模式生成的POJO，然后尝试使用avro进行序列化以放置在kafka主题上。一些xmlElement是可选的

测试消息如下所示：

@XmlRootElement(name = "message")
public class Testmessage {

  @XmlElement
  public String id;


  @XmlElement
  public String name;

  public Testmessage(String id, String name) {
    this.id = id;
    this.name = name;
  }

  public Testmessage() { }

  @Override
  public String toString() {
    return "Message{" +
        "id='" + id + '\'' +
        ", name=" + name +
        '}';
  }
}

序列化和放置在主题上的方法是：

public void sendMessage(Testmessage msg) throws Exception{

    DatumWriter<Testmessage> writer = new ReflectDatumWriter<Testmessage>(Testmessage.class); 
    ByteArrayOutputStream os = new ByteArrayOutputStream();

    Encoder encoder = EncoderFactory.get().binaryEncoder(os, null);
    writer.write(msg, encoder);
    encoder.flush();
    os.close();
    KeyedMessage<String, byte[]> data = new KeyedMessage<String, byte[]>(TOPIC_NAME, os.toByteArray());

    producer.send(data);

}

当我同时发送两个字段时，所有工作均按预期进行。如果我将其中一个字段设为空或将其遗漏，则会从写入中获得NPE。

java.lang.NullPointerException: in Testmessage in string null of string in field id of    Testmessage
at org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:145)
at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:58)

有任何想法吗？或指出正确的方向

谢谢！

超级蜜蜂

看来发布后我已经设法自己解决了，几天后阅读了互联网

    ReflectData reflectData = ReflectData.AllowNull.get();
    Schema schema = reflectData.getSchema(Testmessage.class);

    DatumWriter<Testmessage> writer = new ReflectDatumWriter<Testmessage>(schema);

似乎很高兴允许使用null。

继续我的下一个错误！这是

org.apache.avro.UnresolvedUnionException: Not in union ["null",{"type":"record","name":"XMLGregorianCalendar","namespace":"javax.xml.datatype","fields":[]}]: 2014-10-22
at org.apache.avro.generic.GenericData.resolveUnion(GenericData.java:604)
at org.apache.avro.generic.GenericDatumWriter.resolveUnion(GenericDatumWriter.java:151)
at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:71)
at org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:143)
at org.apache.avro.generic.GenericDatumWriter.writeField(GenericDatumWriter.java:114)

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